Have a question about digital photography? Send it to me. I reply to as many as I can--though given the quantity of e-mails that I get, I can't promise a personal reply to each one. I round up the most interesting questions about once a month here in Digital Focus. For more frequently asked questions, read my newsletters from April, May, and June.
Rights to Reusing Photos From the Web
Your recent article on creating a time capsule with photos from the Web made me curious about copyright. The school district I work in has been trying to find ways to educate teachers and students about proper use of online photos. Do you have suggestions? Any ideas for copyright-free sources of photos that could be used in school projects?
--Paul Garrett, Richmond, Vermont
Copyright is an important consideration when you attempt to reuse a photo for anything other than personal use. I applaud you for thinking about photo rights at your school. I suggest you check out the Professional Photographers of America--that site has a number of educational resources to help your staff understand copyright as it applies to photos.
If you're looking for royalty free photos you can use in school projects, I highly recommend that you turn to photos published with the Creative Commons license. On Flickr, for example, you can limit your photo searches just to Creative Commons images, and further specify only those photos that you may use commercially and/or modify from their original intent.
I have trouble photographing hummingbirds in my backyard. I am using a 70-300mm zoom lens, and unless the sun is shining directly on the feeder (which is the worst time to take my shot), the light is too low. I know that I need to use a fast shutter speed to freeze the bird in flight, but there is not enough illumination. What is the solution?
--Laura Payne, Dallas, Texas
The simplest solution is to increase your ISO, Laura. Every time you double the ISO, say from 100 to 200 and then from 200 to 400, you double the sensitivity of the sensor to light, allowing you to halve the shutter speed. You add a lot of digital noise to high-ISO photos, though, so it is a balancing act to find the lowest possible ISO that delivers the shutter speed you need.
You may want to invest some money to improve your hummingbird photos, because your zoom lens is almost certainly holding you back. Most common zooms in this range have a maximum aperture around f5/6. That's pretty "slow," and it's the main reason you can't get a good shutter speed except in very bright light. You could investigate a faster lens, such as one that can reach f/4 or better (the smaller the f/stop value, the larger the aperture, and thus the faster the shutter speed).
Unfortunately, most fast telephoto lenses are priced in the stratosphere. If you have $5000 or more, you can get a super-fast f/2.8 telephoto, for example. $1500 can buy you an f/4 telephoto. Check out camera stores and online auctions, though; sometimes you can get used lenses at a real bargain. And read "Demystifying Lenses" for more details on lens speed.
Understanding JPEG Compression
I don't understand how the file size and image quality are related when I save a photo. For example, I can start with a photo that's 4 megabytes, but when I save it at the highest quality level, it ends up even bigger--5 megabytes. How is that even possible?
--Dennis Westlin, Jacksonville, Florida
It's magic, Dennis.
Seriously, it is a little confusing, because of the way that the JPEG file format works. In general terms, JPEG files keep track of the difference in the color between adjacent pixels. when you save a JPEG at a lower quality level, it throws away some of this color information in order to create a smaller file size, which can lead to color "fringing." (The resolution, or number of pixels in the photo, is never affected by the quality setting.)
So it's obvious that if you save a photo with a lower quality, the image size should go down. But if you start with a lower quality image and then save it with higher quality settings, the program saves detailed information about color transitions between pixels even if those color transitions don't really exist--and that can artificially inflate the file size.
Here's an example of how that works in real life: Your digital camera is probably set at the factory to save its photos at a medium quality level. If you later edit that photo on your PC and save it at the highest quality level, you'll end up making the file bigger.
As an aside, I highly recommend digging into your camera settings and making sure it saves its photos at the highest possible quality level.
Free Photo Editors With Layers
Do any free photo editing programs have layers?
--Bob Castaldi, Orlando, Florida
Absolutely, Bob. I've written about the GNU Image Manipulation Program (GIMP) a few times over the years, and that program has full layer support. If you want to edit your photos online, you might also want to check out Splashup, a Web-based photo editor that has layer support as well.
Shooting Inside Cathedrals
I experience "bad lighting" even in the middle of the day, since I enjoy shooting inside of huge European cathedrals. When shopping for a camera, I assume my highest priority should be sensitivity in low-light conditions. What do you recommend?
--E. Douglas Jensen, Natick, Massachusetts
Yes, the ability to shoot with a high ISO can be helpful, but getting good cathedral shots generally requires you to mount your camera on a tripod or monopod and taking a short time exposure at a slow shutter speed. You might want to check out my article on photography inside museums and cathedrals. Also, my advice to Laura about shooting hummingbirds at the beginning of this column applies to you as well--the camera itself is not as important as using the fastest lens you can afford.
Hot Pic of the Week
Get published, get famous! Each week, we select our favorite reader-submitted photo based on creativity, originality, and technique.
Here's how to enter: Send us your photograph in JPEG format, at a resolution no higher than 640 by 480 pixels. Entries at higher resolutions will be immediately disqualified. If necessary, use an image editing program to reduce the file size of your image before e-mailing it to us. Include the title of your photo along with a short description and how you photographed it. Don't forget to send your name, e-mail address, and postal address. Before entering, please read the full description of the contest rules and regulations.
This Week's Hot Pic: "Country Spokes," by Ron Berkley, Spokane Valley, Washington
Ron writes: "This is an old wagon wheel in front of a local restaurant in my town. I photographed it on an overcast day so there would be no shadows in the shot, using a Fuji FinePix S1000FD."
This Week's Runner-Up: "Poles," by William Egan, Lutherville, Maryland
William says: "I took this photo using the camera on my iPhone. I was on a fishing trip in the Chesapeake Bay, trolling with 26 lines out. The sun was casting a nice hue on the rods so I got under them to capture the vertical pattern. The IPhone warped the image slightly, which is how the fish eye effect was created."
This story, "Frequently Asked Photo Questions for July" was originally published by PCWorld.